ABSTRACT. Histology and histochemical characterization of the digestive tract of Pimelodus maculatus (Pimelodidae, Siluriformes) in Funil reservoir, Rio de Janeiro, Brazil. Histological structures of the digestive traits of Pimelodus maculatus La Cepède, 1803, in the Funil reservoir (22º30'-22º35'S; 44º35'-44º40'W) were described using haematoxilin-eosin (HE), trichome Gomori, periodic acid Schiff (PAS) and alcian blue (AB) pH 2.5 techniques. The main aim of this study was to detect the levels of glycoproteins (GPs) in the mucous tunic based in histochemical techniques and to characterize eventual alteration in the digestive tract of this species in a polluted system. Fifty-four adult individuals collected between April-2003 and July-2004 (TL=19-38 cm) were examined. The mucosa showed longitudinal folds in the buccopharyngeal cavity, with a stratified squamous epithelium. The oesophagus showed epithelium similar to buccopharyngeal cavity, with a predominance of mucous cells, which reacted strongly with the used methods. The stomach showed three regions: cardic, fundic and pyloric. The mucous tunic is continuously revested by a single cylindrical epithelium which showed positive reaction to AB and PAS only at the apical cells surface. The proper tunic has tubular glands that ramify gradatively, being a cellular type named oxyntopeptic, related to chloridric acid and pepsinogenic cells synthesis. The intestine showed vilosities, with the mucous tunic revested by a single cylindrical epithelium with striated planure and caliciform cells. The duodenum submucosa layer was located at the coledocum opening, as a single cylindrical epithelium lacking caliciforms cells, reacting positively with both PAS and AB. The eutrophic environment of Funil reservoir did not seem to influence morphologic patterns of the structures (oesophagus, stomach and intestine) and no modification was observed in the mucous cells activity. KEYWORDS.Morphology, glycoproteins, fishes, Pimelodidae. RESUMO. As estruturas teciduais do trato gastrintestinal dePimelodus maculatus La Cepède, 1803, do reservatório de Funil (22º30'-22º35'S; 44º35'-44º40'W) foram descritas através das técnicas de hematoxilina-eosina (HE), tricômico Gomori, ácido Periódico de Schiff (PAS) e alcian blue (AB) pH 2,5. Objetivou-se a detecção de glicoproteínas (GPs) na mucosa através de uma análise histoquímica e caracterização de possíveis alterações ao longo do trato digestório destes peixes neste sistema de elevado grau de alteração. Cinqüenta e quatro indivíduos adultos, coletados entre abril de 2003 e julho de 2004 (CT=19-38 cm) foram utilizados. Na cavidade bucofaríngea, a mucosa apresenta-se com pregas longitudinais e o epitélio é do tipo estratificado pavimentoso. O esôfago apresenta o mesmo tipo de epitélio da cavidade bucofaríngea, destacando-se a predominância de células mucosas que tiveram forte reação aos métodos utilizados. O estômago foi diferenciado em região cárdica, fúndica e pilórica. A mucosa é continuamente revestida por um epitélio simples cilíndrico que...